// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/filters/h265_parser.h"

#include <stddef.h>

#include "base/logging.h"
#include "base/stl_util.h"
#include "media/base/decrypt_config.h"

namespace media {

#define READ_BITS_OR_RETURN(num_bits, out)                                       \
    do {                                                                         \
        int _out;                                                                \
        if (!br_.ReadBits(num_bits, &_out)) {                                    \
            DVLOG(1)                                                             \
                << "Error in stream: unexpected EOS while trying to read " #out; \
            return kInvalidStream;                                               \
        }                                                                        \
        *out = _out;                                                             \
    } while (0)

#define TRUE_OR_RETURN(a)                                                  \
    do {                                                                   \
        if (!(a)) {                                                        \
            DVLOG(1) << "Error in stream: invalid value, expected " << #a; \
            return kInvalidStream;                                         \
        }                                                                  \
    } while (0)

H265NALU::H265NALU()
{
    memset(this, 0, sizeof(*this));
}

H265Parser::H265Parser()
{
    Reset();
}

H265Parser::~H265Parser()
{
}

void H265Parser::Reset()
{
    stream_ = NULL;
    bytes_left_ = 0;
    encrypted_ranges_.clear();
}

void H265Parser::SetStream(const uint8_t* stream, off_t stream_size)
{
    std::vector<SubsampleEntry> subsamples;
    SetEncryptedStream(stream, stream_size, subsamples);
}

void H265Parser::SetEncryptedStream(
    const uint8_t* stream,
    off_t stream_size,
    const std::vector<SubsampleEntry>& subsamples)
{
    DCHECK(stream);
    DCHECK_GT(stream_size, 0);

    stream_ = stream;
    bytes_left_ = stream_size;

    encrypted_ranges_.clear();
    const uint8_t* start = stream;
    const uint8_t* stream_end = stream_ + bytes_left_;
    for (size_t i = 0; i < subsamples.size() && start < stream_end; ++i) {
        start += subsamples[i].clear_bytes;

        const uint8_t* end = std::min(start + subsamples[i].cypher_bytes, stream_end);
        encrypted_ranges_.Add(start, end);
        start = end;
    }
}

bool H265Parser::LocateNALU(off_t* nalu_size, off_t* start_code_size)
{
    // Find the start code of next NALU.
    off_t nalu_start_off = 0;
    off_t annexb_start_code_size = 0;

    if (!H264Parser::FindStartCodeInClearRanges(stream_, bytes_left_,
            encrypted_ranges_,
            &nalu_start_off,
            &annexb_start_code_size)) {
        DVLOG(4) << "Could not find start code, end of stream?";
        return false;
    }

    // Move the stream to the beginning of the NALU (pointing at the start code).
    stream_ += nalu_start_off;
    bytes_left_ -= nalu_start_off;

    const uint8_t* nalu_data = stream_ + annexb_start_code_size;
    off_t max_nalu_data_size = bytes_left_ - annexb_start_code_size;
    if (max_nalu_data_size <= 0) {
        DVLOG(3) << "End of stream";
        return false;
    }

    // Find the start code of next NALU;
    // if successful, |nalu_size_without_start_code| is the number of bytes from
    // after previous start code to before this one;
    // if next start code is not found, it is still a valid NALU since there
    // are some bytes left after the first start code: all the remaining bytes
    // belong to the current NALU.
    off_t next_start_code_size = 0;
    off_t nalu_size_without_start_code = 0;
    if (!H264Parser::FindStartCodeInClearRanges(nalu_data, max_nalu_data_size,
            encrypted_ranges_,
            &nalu_size_without_start_code,
            &next_start_code_size)) {
        nalu_size_without_start_code = max_nalu_data_size;
    }
    *nalu_size = nalu_size_without_start_code + annexb_start_code_size;
    *start_code_size = annexb_start_code_size;
    return true;
}

H265Parser::Result H265Parser::AdvanceToNextNALU(H265NALU* nalu)
{
    off_t start_code_size;
    off_t nalu_size_with_start_code;
    if (!LocateNALU(&nalu_size_with_start_code, &start_code_size)) {
        DVLOG(4) << "Could not find next NALU, bytes left in stream: "
                 << bytes_left_;
        return kEOStream;
    }

    nalu->data = stream_ + start_code_size;
    nalu->size = nalu_size_with_start_code - start_code_size;
    DVLOG(4) << "NALU found: size=" << nalu_size_with_start_code;

    // Initialize bit reader at the start of found NALU.
    if (!br_.Initialize(nalu->data, nalu->size))
        return kEOStream;

    // Move parser state to after this NALU, so next time AdvanceToNextNALU
    // is called, we will effectively be skipping it;
    // other parsing functions will use the position saved
    // in bit reader for parsing, so we don't have to remember it here.
    stream_ += nalu_size_with_start_code;
    bytes_left_ -= nalu_size_with_start_code;

    // Read NALU header, skip the forbidden_zero_bit, but check for it.
    int data;
    READ_BITS_OR_RETURN(1, &data);
    TRUE_OR_RETURN(data == 0);

    READ_BITS_OR_RETURN(6, &nalu->nal_unit_type);
    READ_BITS_OR_RETURN(6, &nalu->nuh_layer_id);
    READ_BITS_OR_RETURN(3, &nalu->nuh_temporal_id_plus1);

    DVLOG(4) << "NALU type: " << static_cast<int>(nalu->nal_unit_type)
             << " at: " << reinterpret_cast<const void*>(nalu->data)
             << " size: " << nalu->size;

    return kOk;
}

} // namespace media
